Conventional melt processing techniques for forming articles of thermoplastic polymers cannot be utilized when using synthetic resins that lack melt viscosity or have a high melt viscosity. Instead, such non-melt processible polymers are typically cast into shaped articles through application of pressure to powders. Common techniques include direct forming, hot compression molding, and isostatic pressing. Isostatic pressing is used in highly demanding applications because it provides isotropic properties.
Conventional isostatic pressing techniques include encapsulating a polymeric material in an encapsulant followed by applying isostatic pressure on the encapsulated polymeric material. For example, in the case of cold isostatic pressing (CIP), a polymeric material may be placed in a rubber bag that is evacuated and subsequently subjected to isostatic external pressures. Conventional hot isostatic pressing (HIP) techniques include encapsulating a polymeric material in a metal can (Japanese patent no. JP63281809A) or include submersing in a low melt alloy (Canadian patent no. CA890515A) or glass followed by the applying isostatic pressure. In the case of a HIP process, the encapsulated polymeric material is also heated.
Such pressing techniques often produce waste, such as waste from encapsulants. In the case of submersion techniques, additional chemical handling and article cleaning produce both chemical waste and additional processing steps.
As such, an improved processing technique for non-melt processible polymers would be desirable.